Converting an Existing Borehole Pump to Solar: Options and Costs

If your borehole is already producing water but your electricity bill is climbing — or load-shedding keeps cutting your supply — converting to solar power is a reasonable thing to investigate. The borehole itself stays in the ground; what changes is the pump, the power source, or both. This article walks through the retrofit options, what typically drives costs, and when it makes more sense to start fresh rather than patch an older system.

What a solar retrofit actually involves

A grid-connected borehole pump runs on AC power — either directly from the mains or via a standard pressure switch and control box. Solar pumping systems, by contrast, usually run on DC power or use an inverter to convert solar DC into AC. A retrofit therefore means one of three things:

1. Replacing only the pump with a DC solar-compatible submersible and adding a solar array and controller.
2. Keeping the existing AC pump and adding a solar inverter and panels to supply it — sometimes called a solar-to-AC solution.
3. A hybrid setup that runs on solar when available and switches to grid or a battery bank when not.

Which route makes sense depends on the condition and age of your current pump, its wattage, and how deep your borehole sits. A pump that is already several years old and due for replacement anyway is usually better swapped out for a purpose-built solar pump rather than bolted onto an inverter. A relatively new, well-matched AC pump may justify the inverter route to protect that capital spend.

You can read more about borehole drilling and full system options if you are still at the stage of deciding whether a borehole is right for your property at all.

Pump compatibility: the first thing to check

Before pricing anything, a qualified installer should assess:

• Motor type and wattage. DC solar pumps are purpose-built for variable voltage from panels. Standard AC submersibles can be paired with a solar inverter, but only if the inverter is rated for the motor’s starting current, which is typically two to three times the running current.
• Borehole depth and dynamic water level. Deeper boreholes require pumps with higher head ratings, which in turn need more panels or a larger array. A pump that was adequately sized for grid power may need reassessment if the solar array can’t reliably deliver peak voltage during winter or heavily overcast periods.
• Casing diameter. Most residential boreholes in South Africa are 6-inch (150 mm) casing. This accommodates the majority of submersible pump diameters on the market, but it is worth confirming before ordering a replacement unit.
• Pump age and condition. A pump that has been in service for more than seven to ten years may have worn components. Pulling it to inspect — and potentially replace — before commissioning a new power system makes practical sense.

What a solar retrofit typically costs

Prices depend heavily on system size, panel count, controller type, whether a battery buffer tank or pressure vessel is included, and regional labour rates. Using Johannesburg as a reference point:

• Borehole pump replacement alone (submersible, installed) typically runs R15,000–R35,000.
• A basic solar kit for a borehole pump — panels, MPPT controller, wiring, installation — adds cost on top of that, with the total varying significantly based on pump wattage and how many panels are required.
• Full solar-powered borehole systems (drilling included) in Johannesburg typically range from R40,000 to R150,000, with most falling between R60,000 and R100,000, depending on depth and equipment.
• A retrofit on an existing borehole naturally avoids the drilling cost, which is often the largest single line item, so you should be working with a meaningfully smaller number — but get itemised quotes to confirm what applies in your area and for your specific setup.

For context on what your pump alone draws from the grid, the post on borehole pump electricity usage gives a practical breakdown that helps you size a solar array without over-specifying.

Unsure whether your current pump is worth keeping or better replaced as part of a solar upgrade? Compare 3 free quotes — vetted installers, no obligation.

Solar-only vs hybrid: which suits most homes?

A pure solar setup — no grid connection, no batteries — is the lowest-cost option but means no pumping at night or during extended overcast periods. For irrigation or topping up a storage tank during daylight hours, this is often perfectly adequate. A 5,000-litre tank filled during the day covers most household needs through the night without any battery spend.

A hybrid system that can draw from the grid or a battery bank when solar output is insufficient costs more upfront but gives you effectively continuous supply. If your household depends on borehole water as its primary or sole source, the extra resilience is usually worth pricing in.

Battery storage for borehole pump systems is a developing area and costs vary substantially by battery chemistry and capacity. Ask installers to quote both scenarios so you can judge the payback difference honestly.

When replacement beats retrofit

Retrofitting is not always the right call. Consider a full pump replacement — and price it as part of the solar project — when:

• The existing pump is over eight years old or has a history of faults.
• It is over- or under-specified for your actual yield (a common issue when properties change use).
• The pump wattage is high enough that the inverter required to run it on solar costs almost as much as a new DC solar pump.
• You are upgrading from a single-phase to a three-phase supply, or vice versa, which changes the motor specification entirely.

The post comparing pump installation vs replacement goes into this decision in more detail and is worth reading before you brief an installer.

Ready to get actual numbers for your borehole's solar conversion? Request quotes from three vetted installers — it's free and there's no commitment to proceed.

Panels, controllers and what to specify

The solar array for a borehole pump is sized to the pump’s wattage, the pumping hours you need per day, your location’s peak sun hours, and a sensible safety margin for cloudy days. As a rough guide, a 750-watt pump might be paired with a 1,200–1,500 W array to allow for panel degradation and overcast conditions, but your installer should run the numbers for your specific latitude and pump curve.

MPPT (Maximum Power Point Tracking) controllers are the current standard for solar pump applications — they extract more usable power from panels across varying light conditions than older PWM controllers. Specify MPPT unless there is a clear cost reason to do otherwise.

For systems that also run other home loads via solar, the question of whether the pump shares the home’s inverter or has a dedicated array is a detailed design conversation. The article on solar-powered boreholes in Johannesburg covers this integration in more depth.

Quality standards and what to ask installers

Water quality from the borehole itself is unaffected by how the pump is powered, but make sure any new pump and pipework materials are appropriate for your water chemistry. Borehole water in many parts of South Africa can be hard or have elevated iron content, which affects pump longevity and seal selection.

All electrical work on the solar array and control system should comply with South African wiring standards and, where applicable, connection rules set by your local distributor. Ask your installer for the relevant compliance certificate on completion. Equipment quality matters: pumps and controllers from reputable suppliers with local technical support are worth paying a modest premium for, given the cost of pulling a failed submersible from a deep borehole.

SANS 241 (2024 edition) governs drinking-water quality standards in South Africa — if the borehole supplies potable water, treatment and testing remain separate considerations from the power conversion, and should not be overlooked when budgeting the full project.